GENEVA - Concentrations of greenhouse gases, the major cause of global warming, are at their highest levels ever recorded and are still climbing, the U.N. World Meteorological Organization said on Monday.

The head of the agency, Michel Jarraud, said the trend could be pushing the world toward the most pessimistic assessments of the rise in temperatures expected in coming decades and said this underlined the need for urgent action.

(Editing by Jonathan Lynn and Tim Pearce)